Behaviour of Light Activities
Shadow play
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When light strikes anything, some
bounces off, some is absorbed ("soaked in") and some may be transmitted
("allowed to pass through"). Sunlight absorbed by furniture, curtains and book-covers fades their colors. Light transmitted by windows makes it possible for us to see through solid brick walls! |
When some light is reflected, some absorbed and some transmitted, a shadow is formed; even a candle flame or a soap bubble casts a shadow. But the darkest shadow is produced when no light gets through a body - such as you. Have you ever tried making shadows shaped like butterflies and rabbits, using only your hands?
A century ago, travellers on the Brocken mountain in Germany were frightened by the appearance of what seemed like giant figures looming in the dawn mists. They were scared by a misjudgement of the size of their own shadows, projected on the mists by the rising sun.
Shadows can frighten because they are not always quite like the ordinary, non-frightening objects that make them.
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Experiment with a pencil fixed to a
long pin, and a bright flashlight, to see the different-shaped shadows possible with this
simple object. Can you make the shadow circular or much bigger than the actual size of the
pencil? Also observe shadows out of doors. Can you separate yourself from your shadow? (Try jumping.) A similar effect to shadows is produced when you see the dark silhouettes of objects, such as trees, against a lighter background. These shapes can be scary too. |
A Magic Room (Pinhole Camera)
| In ancient Egypt a poor farmer was put into prison for upsetting the king. His cell was a small, box-like room with a hole in the wall, to let in air. The walls were coated with white plaster. After some time in this unpleasant place, the farmer thought that he must be going crazy. He could see faint-colored pictures of yellow desert, green trees and blue sky. The clouds were moving. But everything was happening upside-down. |
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Being an intelligent man (perhaps that is why he annoyed the king), he understood the pale and dark pictures. They were produced by light passing through the hole and spreading out to hit the opposite part of the cell.
The prisoner offered to build a "Magic Room" to amuse the king - and, for this, he was given his freedom and enough money to live a more comfortable life.
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Build a magic room (a pinhole
camera) from a cardboard box measuring about 12 x 9 x 9 in. Paint it black inside and plug
any holes. The picture shows where you must paste a white paper screen. Cut a rough hole
(1 in square) in the side opposite the screen. Prick a neat tiny pinhole in a piece of
black cardboard and tape this card over the rough hole - with the pinhole in the middle.
Light will enter the box through the hole. You also need a very dark cloth. Cover yourself with the cloth. Hold the box, with its open side towards you, and drape the cloth around and under the box - forming a sort of room, with you inside and where light can enter only through the hole. |
Point the hole at some brilliant scenery and be amazed by the dim, but colored and moving, upside-down pictures on the screen. Get somebody to help with the cloth.
Construction Paper Photography
Place the different objects on the construction paper and leave the paper in strong summer sunlight. The areas of the paper that are not covered are "exposed." They are faded by the energy from the sunlight. Darker shadow shapes of the objects will be left on the unexposed areas. This is a very simple form of photography.
YOU NEED: • a piece of construction paper • a selection of household objects, such as
a fork, |
